I'm currently in my 20s, and while I don't know the reasoning for others, I have my own reasons for being aroused by the older/younger dynamic. One of the first movies I ever watched that featured gay sex was the film
Boy Culture. The scene featuring the very sexy
Derek Magyar making love to the elderly man was perhaps what first peaked my interest in the idea of this dynamic.
Then a couple of years ago, I saw a film called
Gerontophilia, where this cute teenage boy named Lake volunteers at a retirement home. While there, he becomes the object of lust for one elderly senile patient which clearly makes him uncomfortable at first. However a few scenes later, after getting high off stolen pills, Lake seeks out the old man, finding him horny in bed, and proceeds to seduce him by getting naked in front of him and climbing into his bed.
View attachment Gerontophilia - Patient Clip 01.mp4
View attachment Gerontophilia - Patient Clip 02.mp4
Growing up with such easy access to internet porn has unfortunately made it very difficult for me to orgasm during sex, which has been an issue when having sex with other men my age in the past. However the few times I've been intimate with a man who was perhaps two or three decades older than me, were the times that I actually took note of the fact that I ejaculated; and the older men were completely patient with me, unlike younger guys who seem in a rush to cum.
So for me, I was first attracted to the older/younger dynamic because of seeing those films, which depicted the intimacy between the two partners as very raw and sensual. The contrast of the participants' age somehow made it seem even more erotic in my mind. I'm more turned on by the older/younger dynamic in film and literature, however in reality, my attraction for older men is mostly due to my respect for their ability to be patient and sensual.
Hope that makes sense.